This invention relates to internal combustion engines, and more particularly to a system for supplying fuel to the engine.
In an application Ser. No. 487,156 filed July 10, 1974, now U.S. Pat. No. 3,982,910, by these inventors, which is entitled Hydrogen Rich Gas Generator, there is described and claimed a generator for producing hydrogen rich gas from hydrocarbon fuels. The generator has a catalytic bed containing particles of a partial oxidation catalyst, such as nickel, or platinum or silver oxide. A hydrocarbon fuel is mixed with air and then injected into a chamber where the mixture is ignited using a means, such as a spark plug. The ignited mixture produces a flame and gases which flow through the catalytic bed to heat it up to a required operating temperature. As the catalytic bed heats up beyond 900.degree. F., the flame gradually moves into the catalytic bed and when a steady state temperature of 1800.degree. F. is reached there is no visible flame present and the requirement for igniting the air and hydrocarbon fuel mixture is no longer necessary, since ignition is caused to occur by the hot catalytic bed.
The catalytic bed converts the air and fuel mixture passing therethrough into hydrogen rich product gases which are then collected and mixed with fuel and air which is then fed into the cylinders of the internal combustion engine.
A preferred catalyst is a nickel catalyst. However, the manufacturer of this catalyst recommends that the nickel not be exposed to temperatures above 2200.degree. F. It was previously indicated that start up requires first igniting gases with a burner, which gases are passed through the catalytic bed until it is heated to its light-off temperature, (the temperature at which the reaction starts). To keep the combustion gas temperature down, a rich combustion mixture is used with the flame temperatures on the order of 3000.degree. F. (hence the possibility that some of the catalyst is heated to higher than the 2200.degree. F. maximum). The 3000.degree. F. corresponds to an air/fuel mass ratio of approximately 10. To produce a lower temperature combustion requires using a lower air/fuel ratio. However, it is not feasible to use air/fuel ratios below 10 as this results in soot formation. Soot deposition on a catalyst, in turn, results in catalyst deactivation and can also cause plugging of gas passages in the catalyst. Further, the temperature above 2300.degree. F., causes a degradation of the catalyst active surface so that some capability is lost with each cold start of the generator.
When a sufficient amount of catalyst surface has been heated above the light off temperature (800.degree. -1000.degree. F range for a nickel catalyst), the air/fuel ratio must be changed from the cold start value of 10 to the operating value of 5.2. This procedure will then cause the transition from a luminous start-up flame to flameless operation within the catalyst bed. Switching the air/fuel ratio from 10 to 5.2 during start-up requires an appropriate control system which adds to the overall complexity and which reduces the overall reliability.
Accordingly, a start-up system which would avoid overheating the catalyst and the need for apparatus for changing the air/fuel ratio from a start-up value to an operating value would result in a less expensive catalytic converter, as well as one which avoids the possibility of damage or plugging of the catalytic converter bed.